Graphene compositions

ABSTRACT

Compositions comprising graphene sheets, at least one binder, and a carrier system, wherein about 1 to about 50 weight percent of the carrier system comprises at least one cyclic amide, cyclic imide, and/or lactone. The compositions may be used as coatings and inks.

REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional ApplicationNo. 61/320,732, filed Apr. 3, 2010, the entire contents of which arehereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to compositions comprising graphenesheets, at least one binder, and a carrier system comprising at leastone cyclic amide, cyclic imide, and/or lactone.

BACKGROUND

Surface coatings can be used to impart articles with desirableproperties that are not possessed by the articles themselves or notpossessed in a sufficient degree. For example, there are myriadapplications for which it would be desirable to use electricallyconductive and/or thermally conductive components having good physicalproperties. Because of their intrinsic conductivities and frequentlyadvantageous physical properties, metals are often useful for suchapplications but can have drawbacks, including increased weight, cost,and that they can be difficult and/or inconvenient to form into avariety of shapes, including intricate parts. Furthermore, metalliccoatings can require high curing temperatures and/or prolonged curingtimes, which can be harmful to many substrates, such as some papers,polymers, adhesives, etc.

Many of these drawbacks can be overcome by the use of polymericmaterials, which can have cost, weight, processability, and flexibilityof design advantages over metals. However, most polymeric materials arenot intrinsically conductive enough for many applications and conductiveadditives must often be used to achieve the desired properties. Highloadings are often required to get useful conductivities, which can beto the detriment of physical and other properties of the materials andcan interfere with the processability of the polymers. Furthermore, manypolymer-based coatings require curing conditions (such temperatures andtimes) that are also incompatible with many substrates. It wouldtherefore be desirable to obtain polymer based compositions that haveimproved conductivity.

SUMMARY OF THE INVENTION

Disclosed and claimed herein are compositions comprising graphenesheets, at least one binder, and a carrier system, wherein about 1 toabout 50 weight percent of the carrier system comprises at least onecyclic amide, cyclic imide, and/or lactone. Further disclosed andclaimed are a method of coating a substrate, comprising applying to asurface of the substrate at least one ink or coating comprising graphenesheets, at least one lactone and/or at least one cyclic amide, and atleast one binder and articles comprising a surface coated with at leastone ink or coating comprising graphene sheets, at least one lactoneand/or at least one cyclic amide, and at least one binder.

DETAILED DESCRIPTION OF THE INVENTION

The compositions comprise graphene sheets, at least one binder, and acarrier system that comprises at least one cyclic amide, cyclic imide,and/or lactone. The compositions may be in the form of inks or coatings.

The cyclic amides, cyclic imides, and lactones preferably have boilingpoints of no greater than about 300° C., or more preferably of nogreater than about 250° C., or yet more preferably of no greater thanabout 220° C. Examples of cyclic amides include N-methylpyrrolidone(N-methyl-2-pyrrolidone), pyrrolidone, etc. Examples of lactonesinclude, but are not limited to, lactones with 4- to 8-membered rings.Examples of lactones include beta-propiolactone, gamma-valerolactone,delta-valerolactone, gamma-butyrolactone, epsilon-caprolactone, etc.Examples of cyclic imides include imidazolidinones such asN,N′-dimethylimidazolidinone (1,3-dimethyl-2-imidazolidinone).

There are no particular limitations to the components that comprise theremainder of the carrier system. Examples of suitable carriers include,but are not limited to, one or more of water, organic solvents,distilled or synthetic isoparaffinic hydrocarbons (such Isopar® andNorpar® (both manufactured by Exxon) and Dowanol® (manufactured by Dow),citrus terpenes and mixtures containing citrus terpenes (such asPurogen, Electron, and Positron (all manufactured by Ecolink)), terpenesand terpene alcoholds (including terpineols, including alpha-terpineol),limonene, aliphatic petroleum distillates, alcohols (such as methanol,ethanol, n-propanol, i-propanol, n-butanol, butanol, sec-butanol,tert-butanol, pentanols, i-amyl alcohol, hexanols, heptanols, octanols,diacetone alcohol, butyl glycol, etc.), ketones (such as acetone, methylethyl ketone, cyclohexanone, i-butyl ketone, 2,6,8,trimethyl-4-nonanoneetc.), esters (such as methyl acetate, ethyl acetate, n-propyl acetate,i-propyl acetate, n-butyl acetate, i-butyl acetate, tert-butyl acetate,carbitol acetate, etc.), glycol ethers, ester and alcohols (such as2-(2-ethoxyethoxy)ethanol, propylene glycol monomethyl ether and otherpropylene glycol ethers; ethylene glycol monobutyl ether, 2-methoxyethylether (diglyme), propylene glycol methyl ether (PGME); and otherethylene glycol ethers; ethylene and propylene glycol ether acetates,diethylene glycol monoethyl ether acetate, 1-methoxy-2-propanol acetate(PGMEA); and hexylene glycol (such as Hexasol™ (supplied bySpecialChem)), imides, amides (such as dimethylacetamide), dibasicesters (such as dimethyl succinate, dimethyl glutarate, dimethyladipate), etc. Solvents may be low- or non-VOC solvents, non-hazardousair pollution solvents, and non-halogenated solvents.

The cyclic amide, cyclic imide, and/or lactone component comprises fromabout 0.1 to about 50 weight percent of the carrier systems. In someembodiments, the cyclic amide, cyclic imide, and/or lactone componentmay comprise from about 0.1 to about 40 percent, or from about 0.1 toabout 30 percent, or from about 1 to about 50 percent, or from about 1to about 40 percent, or from about 1 to about 30 percent, or from about1 to about 25 percent, or from about 1 to about 20 percent, or fromabout 1 to about 15 percent, or from about 1 to about 10 percent, orfrom about 5 to about 50 percent, or from about 5 to about 40 percent,from about 5 to about 30 percent, or from about 5 to about 20 percent,or from about 5 to about 10 percent, or from about 3 to about 10percent, or from about 3 to about 20 percent of the carrier system, orfrom about 3 to about 30 percent, or from about 3 to about 40 percent,or from about 3 to about 50 percent, or from about 2 to about 10percent, or from about 2 to about 20 percent, or from 2 to about 30percent, or from about 2 to about 40 percent, or from about 2 to about50 percent of the carrier system, where all percentages are weightpercentages.

The graphene sheets are graphite sheets preferably having a surface areaof from about 100 to about 2630 m²/g. In some embodiments, the graphenesheets primarily, almost completely, or completely comprise fullyexfoliated single sheets of graphite (these are approximately 1 nm thickand are often referred to as “graphene”), while in other embodiments, atleast a portion of the graphene sheets may comprise at partiallyexfoliated graphite sheets, in which two or more sheets of graphite havenot been exfoliated from each other. The graphene sheets may comprisemixtures of fully and partially exfoliated graphite sheets.

Graphene sheets may be made using any suitable method. For example, theymay be obtained from graphite, graphite oxide, expandable graphite,expanded graphite, etc. They may be obtained by the physical exfoliationof graphite, by for example, peeling off sheets graphene sheets. Theymay be made from inorganic precursors, such as silicon carbide. They maybe made by chemical vapor deposition (such as by reacting a methane andhydrogen on a metal surface). They may be may by the reduction of analcohol, such ethanol, with a metal (such as an alkali metal likesodium) and the subsequent pyrolysis of the alkoxide product (such amethod is reported in Nature Nanotechnology (2009), 4, 30-33). They maybe made by the exfoliation of graphite in dispersions or exfoliation ofgraphite oxide in dispersions and the subsequently reducing theexfoliated graphite oxide. Graphene sheets may be made by theexfoliation of expandable graphite, followed by intercalation, andultrasonication or other means of separating the intercalated sheets(see, for example, Nature Nanotechnology (2008), 3, 538-542). They maybe made by the intercalation of graphite and the subsequent exfoliationof the product in suspension, thermally, etc.

Graphene sheets may be made from graphite oxide (also known as graphiticacid or graphene oxide). Graphite may be treated with oxidizing and/orintercalating agents and exfoliated. Graphite may also be treated withintercalating agents and electrochemically oxidized and exfoliated.Graphene sheets may be formed by ultrasonically exfoliating suspensionsof graphite and/or graphite oxide in a liquid (which may containsurfactants and/or intercalants). Exfoliated graphite oxide dispersionsor suspensions can be subsequently reduced to graphene sheets. Graphenesheets may also be formed by mechanical treatment (such as grinding ormilling) to exfoliate graphite or graphite oxide (which wouldsubsequently be reduced to graphene sheets).

Reduction of graphite oxide to graphene may be by means of chemicalreduction and may be carried out in graphite oxide in a solid form, in adispersion, etc. Examples of useful chemical reducing agents include,but are not limited to, hydrazines (such as hydrazine,N,N-dimethylhydrazine, etc.), sodium borohydride, citric acid,hydroquinone, isocyanates (such as phenyl isocyanate), hydrogen,hydrogen plasma, etc. A dispersion or suspension of exfoliated graphiteoxide in a carrier (such as water, organic solvents, or a mixture ofsolvents) can be made using any suitable method (such as ultrasonicationand/or mechanical grinding or milling) and reduced to graphene sheets.

Graphite oxide may be produced by any method known in the art, such asby a process that involves oxidation of graphite using one or morechemical oxidizing agents and, optionally, intercalating agents such assulfuric acid. Examples of oxidizing agents include nitric acid, sodiumand potassium nitrates, perchlorates, hydrogen peroxide, sodium andpotassium permanganates, phosphorus pentoxide, bisulfites, etc.Preferred oxidants include KCIO₄; HNO₃ and KCIO₃; KMnO₄ and/or NaMnO₄;KMnO₄ and NaNO₃; K₂S₂O₈ and P₂O₅ and KMnO₄; KMnO₄ and HNO₃; and HNO₃.Preferred intercalation agents include sulfuric acid. Graphite may alsobe treated with intercalating agents and electrochemically oxidized.Examples of methods of making graphite oxide include those described byStaudenmaier (Ber. Stsch. Chem. Ges. (1898), 31, 1481) and Hummers (J.Am. Chem. Soc. (1958), 80, 1339).

One example of a method for the preparation of graphene sheets is tooxidize graphite to graphite oxide, which is then thermally exfoliatedto form graphene sheets (also known as thermally exfoliated graphiteoxide), as described in US patent application publication 2007/0092432,the disclosure of which is incorporated herein by reference. The thuslyformed graphene sheets may display little or no signature correspondingto graphite or graphite oxide in their X-ray-diffraction pattern.

The thermal exfoliation may be carried out in a continuous,semi-continuous batch, etc. process.

Heating can be done in a batch process or a continuous process and canbe done under a variety of atmospheres, including inert and reducingatmospheres (such as nitrogen, argon, and/or hydrogen atmospheres).Heating times can range from under a few seconds or several hours ormore, depending on the temperatures used and the characteristics desiredin the final thermally exfoliated graphite oxide. Heating can be done inany appropriate vessel, such as a fused silica, mineral, metal, carbon(such as graphite), ceramic, etc. vessel. Heating may be done using aflash lamp.

During heating, the graphite oxide may be contained in an essentiallyconstant location in single batch reaction vessel, or may be transportedthrough one or more vessels during the reaction in a continuous or batchmode. Heating may be done using any suitable means, including the use offurnaces and infrared heaters.

Examples of temperatures at which the thermal exfoliation of graphiteoxide may be carried out are at least about 300° C., at least about 400°C., at least about 450° C., at least about 500° C., at least about 600°C., at least about 700° C., at least about 750° C., at least about 800°C., at least about 850° C., at least about 900° C., at least about 950°C., and at least about 1000° C. Preferred ranges include between about750 about and 3000° C., between about 850 and 2500° C., between about950 and about 2500° C., and between about 950 and about 1500° C.

The time of heating can range from less than a second to many minutes.For example, the time of heating can be less than about 0.5 seconds,less than about 1 second, less than about 5 seconds, less than about 10seconds, less than about 20 seconds, less than about 30 seconds, or lessthan about 1 min. The time of heating can be at least about 1 minute, atleast about 2 minutes, at least about 5 minutes, at least about 15minutes, at least about 30 minutes, at least about 45 minutes, at leastabout 60 minutes, at least about 90 minutes, at least about 120 minutes,at least about 150 minutes, at least about 240 minutes, from about 0.01seconds to about 240 minutes, from about 0.5 seconds to about 240minutes, from about 1 second to about 240 minutes, from about 1 minuteto about 240 minutes, from about 0.01 seconds to about 60 minutes, fromabout 0.5 seconds to about 60 minutes, from about 1 second to about 60minutes, from about 1 minute to about 60 minutes, from about 0.01seconds to about 10 minutes, from about 0.5 seconds to about 10 minutes,from about 1 second to about 10 minutes, from about 1 minute to about 10minutes, from about 0.01 seconds to about 1 minute, from about 0.5seconds to about 1 minute, from about 1 second to about 1 minute, nomore than about 600 minutes, no more than about 450 minutes, no morethan about 300 minutes, no more than about 180 minutes, no more thanabout 120 minutes, no more than about 90 minutes, no more than about 60minutes, no more than about 30 minutes, no more than about 15 minutes,no more than about 10 minutes, no more than about 5 minutes, no morethan about 1 minute, no more than about 30 seconds, no more than about10 seconds, or no more than about 1 second. During the course ofheating, the temperature may vary.

Examples of the rate of heating include at least about 120° C./min, atleast about 200° C./min, at least about 300° C./min, at least about 400°C./min, at least about 600° C./min, at least about 800° C./min, at leastabout 1000° C./min, at least about 1200° C./min, at least about 1500°C./min, at least about 1800° C./min, and at least about 2000° C./min.

Graphene sheets may be annealed or reduced to graphene sheets havinghigher carbon to oxygen ratios by heating under reducing atmosphericconditions (e.g., in systems purged with inert gases or hydrogen).Reduction/annealing temperatures are preferably at least about 300° C.,or at least about 350° C., or at least about 400° C., or at least about500° C., or at least about 600° C., or at least about 750° C., or atleast about 850° C., or at least about 950° C., or at least about 1000°C. The temperature used may be, for example, between about 750 about and3000° C., or between about 850 and 2500° C., or between about 950 andabout 2500° C.

The time of heating can be for example, at least about 1 second, or atleast about 10 second, or at least about 1 minute, or at least about 2minutes, or at least about 5 minutes. In some embodiments, the heatingtime will be at least about 15 minutes, or about 30 minutes, or about 45minutes, or about 60 minutes, or about 90 minutes, or about 120 minutes,or about 150 minutes. During the course of annealing/reduction, thetemperature may vary within these ranges.

The heating may be done under a variety of conditions, including in aninert atmosphere (such as argon or nitrogen) or a reducing atmosphere,such as hydrogen (including hydrogen diluted in an inert gas such asargon or nitrogen), or under vacuum. The heating may be done in anyappropriate vessel, such as a fused silica or a mineral or ceramicvessel or a metal vessel. The materials being heated including anystarting materials and any products or intermediates) may be containedin an essentially constant location in single batch reaction vessel, ormay be transported through one or more vessels during the reaction in acontinuous or batch reaction. Heating may be done using any suitablemeans, including the use of furnaces and infrared heaters.

The graphene sheets preferably have a surface area of at least about 100m²/g to, or of at least about 200 m²/g, or of at least about 300 m²/g,or of least about 350 m²/g, or of least about 400 m²/g, or of leastabout 500 m²/g, or of least about 600 m²/g., or of least about 700 m²/g,or of least about 800 m²/g, or of least about 900 m²/g, or of leastabout 700 m²/g. The surface area may be about 400 to about 1100 m²/g.The theoretical maximum surface area can be calculated to be 2630 m²/g.The surface area includes all values and subvalues therebetween,especially including 400, 500, 600, 700, 800, 900, 1000, 1100, 1200,1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400,2500, and 2630 m²/g.

The graphene sheets can have number average aspect ratios of about 100to about 100,000, or of about 100 to about 50,000, or of about 100 toabout 25,000, or of about 100 to about 10,000 (where “aspect ratio” isdefined as the ratio of the longest dimension of the sheet to theshortest).

Surface area can be measured using either the nitrogen adsorption/BETmethod at 77 K or a methylene blue (MB) dye method in liquid solution.

The dye method is carried out as follows: A known amount of graphenesheets is added to a flask. At least 1.5 g of MB are then added to theflask per gram of graphene sheets. Ethanol is added to the flask and themixture is ultrasonicated for about fifteen minutes. The ethanol is thenevaporated and a known quantity of water is added to the flask tore-dissolve the free MB. The undissolved material is allowed to settle,preferably by centrifuging the sample. The concentration of MB insolution is determined using a UV-vis spectrophotometer by measuring theabsorption at λ_(max)=298 nm relative to that of standardconcentrations.

The difference between the amount of MB that had been initially addedand the amount present in solution as determined by UV-visspectrophotometry is assumed to be the amount of MB that has beenadsorbed onto the surface of the graphene sheets. The surface area ofthe graphene sheets are then calculated using a value of 2.54 m² ofsurface covered per one mg of MB adsorbed.

The graphene sheets may have a bulk density of from about 0.1 to atleast about 200 kg/m³. The bulk density includes all values andsubvalues therebetween, especially including 0.5, 1, 5, 10, 15, 20, 25,30, 35, 50, 75, 100, 125, 150, and 175 kg/m³.

The graphene sheets may be functionalized with, for example,oxygen-containing functional groups (including, for example, hydroxyl,carboxyl, and epoxy groups) and typically have an overall carbon tooxygen molar ratio (C/O ratio), as determined by elemental analysis ofat least about 1:1, or more preferably, at least about 3:2. Examples ofcarbon to oxygen ratios include about 3:2 to about 85:15; about 3:2 toabout 20:1; about 3:2 to about 30:1; about 3:2 to about 40:1; about 3:2to about 60:1; about 3:2 to about 80:1; about 3:2 to about 100:1; about3:2 to about 200:1; about 3:2 to about 500:1; about 3:2 to about 1000:1;about 3:2 to greater than 1000:1; about 10:1 to about 30:1; about 80:1to about 100:1; about 20:1 to about 100:1; about 20:1 to about 500:1;about 20:1 to about 1000:1; about 50:1 to about 300:1; about 50:1 toabout 500:1; and about 50:1 to about 1000:1. In some embodiments, thecarbon to oxygen ratio is at least about 10:1, or at least about 20:1,or at least about 35:1, or at least about 50:1, or at least about 75:1,or at least about 100:1, or at least about 200:1, or at least about300:1, or at least about 400:1, or at least 500:1, or at least about750:1, or at least about 1000:1; or at least about 1500:1, or at leastabout 2000:1. The carbon to oxygen ratio also includes all values andsubvalues between these ranges.

The graphene sheets may contain atomic scale kinks. These kinks may becaused by the presence of lattice defects in, or by chemicalfunctionalization of the two-dimensional hexagonal lattice structure ofthe graphite basal plane.

The compositions may further comprise graphite (including natural, Kish,and synthetic, annealed, pyrolytic, highly oriented pyrolytic, etc.graphites). The ratio by weight of graphite to graphene sheets may befrom about 2:98 to about 98:2, or from about 5:95 to about 95:5, or fromabout 10:90 to about 90:10, or from about 20:80 to about 80:20, or fromabout 30:70 to 70:30, or from about 40:60 to about 90:10, or from about50:50 to about 85:15, or from about 60:40 to about 85:15, or from about70:30 to about 85:15.

The graphene sheets may comprise two or more graphene powders havingdifferent particle size distributions and/or morphologies. The graphitemay also comprise two or more graphite powders having different particlesize distributions and/or morphologies.

The binders can be thermoplastics or thermosets and may be elastomers.Binders may also comprise monomers that can be polymerized before,during, or after the application of the ink or coating to the substrate.Polymeric binders may be crosslinked or otherwise cured after the ink orcoating has been applied to the substrate. Examples of polymeric bindersinclude polysiloxanes (such as poly(dimethylsiloxane),dimethylsiloxane/vinylmethylsiloxane copolymers, vinyldimethylsiloxaneterminated poly(dimethylsiloxane), etc.), polyethers and glycols such aspoly(ethylene oxide)s (also known as poly(ethylene glycol)s,poly(propylene oxide)s (also known as poly(propylene glycol)s, andethylene oxide/propylene oxide copolymers, cellulosic resins (such asethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose,cellulose acetate, cellulose acetate propionates, and cellulose acetatebutyrates, nitrocellulose), and poly(vinyl butyral), poly(vinyl acetate)and poly(vinyl acetate) copolymers, poly(vinyl pyrrolidone) andpoly(vinyl pyrrolidone) copolymers, vinyl acetate and vinyl pyrrolidonecopolymers, polyvinyl alcohol and its derivatives, ethylene/vinylacetate polymers, acrylate polymers (such as methyl methacrylatepolymers, methacrylate copolymers, polymers derived from one or moreacrylates, methacrylates, ethyl acrylates, ethyl methacrylates, butylacrylates, butyl methacrylates, glycidyl acrylates and methacrylates andthe like), styrene/acrylic copolymers, styrene/maleic anhydridecopolymers, isobutylene/maleic anhydride copolymers, vinylacetate/ethylene copolymers, ethylene/acrylic acid copolymers,polyolefins, polystyrenes, olefin and styrene copolymers, epoxy resins,acrylic latex polymers, polyester acrylate oligomers and polymers,polyester diol diacrylate polymers, UV-curable resins, and polyamides.Polyamides may be polymers and copolymers (i.e., polyamides having atleast two different repeat units) having melting points between about100 and about 255° C., or between about 120 and about 255° C., orbetween about 110 and about 255° C. or between about 120 and about 255°C. These include aliphatic copolyamides having a melting point of about230° C. or less, aliphatic copolyamides having a melting point of about210° C. or less, aliphatic copolyamides having a melting point of about200° C. or less, aliphatic copolyamides having a melting point of about180° C. or less, of about 150° C. or less, of about 130° C. or less, ofabout 120° C. or less, of about 110° C. or less, etc. Examples of theseinclude those sold under the trade names Macromelt by Henkel, Versamidby Cognis, and Elvamide® by DuPont. Examples of suitable polymersinclude Elvacite® polymers supplied by Lucite International, Inc.,including Elvacite® 2009, 2010, 2013, 2014, 2016, 2028, 2042, 2045,2046, 2550, 2552, 2614, 2669, 2697, 2776, 2823, 2895, 2927, 3001, 3003,3004, 4018, 4021, 4026, 4028, 4044, 4059, 4400, 4075, 4060, 4102, etc.Other polymer families include Bynel® polymers (such as Bynel® 2022supplied by DuPont) and Joncryl® polymers (such as Joncryl® 678 and682).

The graphene sheets and graphite, if present, are preferably present inthe compositions in about 20 to about 98 weight percent, in about 30 toabout 95 weight percent, in about 40 to about 95 weight percent, inabout 50 to about 95 weight percent, and in about 70 to about 95 weightpercent, based on the total amount of graphene sheets and graphite, ifpresent, and binder.

The compositions may be made using any suitable method, including wet ordry methods and batch, semi-continuous, and continuous methods.

For example, components of the coatings, such as one or more of thegraphene sheets, graphite (if used), binders, carriers, and/or othercomponents may be processed (e.g., milled/ground, blended, etc. by usingsuitable mixing, dispersing, and/or compounding techniques andapparatus, including ultrasonic devices, high-shear mixers, ball mills,attrition equipment, sandmills, two-roll mills, three-roll mills,cryogenic grinding crushers, extruders, kneaders, double planetarymixers, triple planetary mixers, high pressure homogenizers, ball mills,attrition equipment, sandmills, horizontal and vertical wet grindingmills, etc. Processing (including grinding) technologies can be wet ordry and can be continuous or discontinuous. Suitable materials for useas grinding media include metals, carbon steel, stainless steel,ceramics, stabilized ceramic media (such as yttrium stabilized zirconiumoxide), PTFE, glass, tungsten carbide, etc. Methods such as these can beused to change the particle size and/or morphology of the graphite,graphene sheets, other components, and blends or two or more components.

Components may be processed together or separately and may go throughmultiple processing (including mixing/blending) stages, each involvingone or more components (including blends).

There is no particular limitation to the way in which the graphenesheets, graphite (if used), and other components are processed andcombined. For example, graphene sheets and/or graphite may be processedinto given particle size distributions and/or morphologies separatelyand then combined for further processing with or without the presence ofadditional components. Unprocessed graphene sheets and/or graphite maybe combined with processed graphene sheets and/or graphite and furtherprocessed with or without the presence of additional components.Processed and/or unprocessed graphene sheets and/or processed and/orunprocessed graphite may be combined with other components, such as oneor more binders and then combined with processed and/or unprocessedgraphene sheets and/or processed and/or unprocessed graphite. Two ormore combinations of processed and/or unprocessed graphene sheets and/orprocessed and/or unprocessed graphite that have been combined with othercomponents may be further combined or processed.

In one embodiment, if a multi-chain lipid is used, it is added tographene sheets (and/or graphite if present) before processing.

After blending and/or grinding steps, additional components may be addedto the compositions, including, but not limited to, thickeners,viscosity modifiers, binders, etc. The compositions may also be dilutedby the addition of more carrier.

The compositions may optionally comprise one or more additionaladditives, such as dispersion aids (including surfactants, emulsifiers,and wetting aids), adhesion promoters, thickening agents (includingclays), defoamers and antifoamers, biocides, additional fillers, flowenhancers, stabilizers, crosslinking and curing agents, etc.

Examples of dispersing aids include glycol ethers (such as poly(ethyleneoxide), block copolymers derived from ethylene oxide and propylene oxide(such as those sold under the trade name Pluronic® by BASF), acetylenicdiols (such as 2,5,8,11-tetramethyl-6-dodecyn-5,8-diol ethoxylate andothers sold by Air Products under the trade names Surfynol® and Dynol®),salts of carboxylic acids (including alkali metal and ammonium salts),and polysiloxanes.

Examples of grinding aids include stearates (such as Al, Ca, Mg, and Znstearates) and acetylenic diols (such as those sold by Air Productsunder the trade names Surfynol® and Dynol®).

Examples of adhesion promoters include titanium chelates and othertitanium compounds such as titanium phosphate complexes (including butyltitanium phosphate), titanate esters, diisopropoxy titaniumbis(ethyl-3-oxobutanoate, isopropoxy titanium acetylacetonate, andothers sold by Johnson-Matthey Catalysts under the trade name Vertec.

Examples of thickening agents include glycol ethers (such aspoly(ethylene oxide), block copolymers derived from ethylene oxide andpropylene oxide (such as those sold under the trade name Pluronic® byBASF), long-chain carboxylate salts (such aluminum, calcium, zinc, etc.salts of stearates, oleats, palmitates, etc.), aluminosilicates (such asthose sold under the Minex® name by Unimin Specialty Minerals andAerosil® 9200 by Evonik Degussa), fumed silica, natural and syntheticzeolites, etc.

The compositions may optionally comprise at least one “multi-chainlipid”, by which term is meant a naturally-occurring or synthetic lipidhaving a polar head group and at least two nonpolar tail groupsconnected thereto. Examples of polar head groups include oxygen-,sulfur-, and halogen-containing, phosphates, amides, ammonium groups,amino acids (including α-amino acids), saccharides, polysaccharides,esters (Including glyceryl esters), zwitterionic groups, etc.

The tail groups may be the same or different. Examples of tail groupsinclude alkanes, alkenes, alkynes, aromatic compounds, etc. They may behydrocarbons, functionalized hydrocarbons, etc. The tail groups may besaturated or unsaturated. They may be linear or branched. The tailgroups may be derived from fatty acids, such as oleic acid, palmiticacid, stearic acid, arachidic acid, erucic acid, arachadonic acid,linoleic acid, linolenic acid, oleic acid, etc.

Examples of multi-chain lipids include, but are not limited to, lecithinand other phospholipids (such as phosphoglycerides (includingphosphatidylserine, phosphatidylinositol, phosphatidylethanolamine(cephalin), and phosphatidylglycerol) and sphingomyelin); glycolipids(such as glucosyl-cerebroside); saccharolipids; sphingolipids (such asceramides, di- and triglycerides, phosphosphingolipids, andglycosphingolipids); etc. They may be amphoteric, includingzwitterionic.

The compositions may optionally comprise one or more charged organiccompounds. The charged organic compound comprises at least one ionicfunctional group and one hydrocarbon-based chain. Examples of ionicfunctional groups include ammonium salts, sulfates, sulphonates,phosphates, carboxylates, etc. If two or more ionic functional groupsare present, they may be of the same or different types. The compoundmay comprise additional functional groups, including, but not limited tohydroxyls, alkenes, alkynes, carbonyl groups (such as carboxylic acids,esters, amides, ketones, aldehydes, anhydrides, thiol, etc.), ethers,fluoro, chloro, bromo, iodo, nitriles, nitrogen containing groups,phosphorous containing groups, silicon containing groups, etc.

The compound comprises at least one hydrocarbon-based chain. Thehydrocarbon-based chain may be saturated or unsaturated and may bebranched or linear. It may be an alkyl group, alkenyl group, alkynylgroup, etc. It need not contain only carbon and hydrogen atoms. It maybe substituted with other functional groups (such as those mentionedabove). Other functional groups, such as esters, ethers, amides, may bepresent in the length of the chain. In other words, the chain maycontain two or more hydrocarbon-based segments that are connected by oneor more functional groups. In one embodiment, at least one ionicfunctional group is located at the end of a chain.

Examples of ammonium salts include materials having the formula:R¹R²R³R⁴N⁺X⁻, where R¹, R², and R³, are each independently H, ahydrocarbon-based chain, an aryl-containing group, an alicyclic group;an oligomeric group, a polymeric group, etc.; where R⁴ is ahydrocarbon-based chain having at least four carbon atoms; and where X⁻is an anion such as fluoride, bromide, chloride, iodide, sulfate,hydroxide, carboxylate, etc. Any of the R groups may have one or moreadditional ammonium groups.

Examples of R groups include methyl, ethyl, propyl, butyl, pentyl,hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl,tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl,eicosyl, C₂₁ to C₄₀ chains, etc.

Examples of quaternary ammonium salts include tetraalkylammonium salts,dialkyldimethylammonium salts, alkyltrimethylammonium salts, where thealkyl groups are one or more groups containing at least eight carbonatoms. Examples include tetradodecylammonium,tetradecyltrimethylammonium halide, hexadecyltrimethylammonium halide,didodecyldimethylammonium halide, etc.

Ammonium salts may be bis- or higher order ammonium salts, includingquaternary ammonium salts. They may be salts of carboxylic acids,dicarboxylic acids, tricarboxylic acids, and higher carboxylic acids.The carboxylic acids may have be part of a hydrocarbon-based chainhaving at least about four linear carbon atoms. Examples includeammonium salts of octanoic acid, nonanoic acid, decanoic acid,undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid,pentadecanic acid, carboxylic acids having at least 15 carbon atoms,stearic acid, oleic acid, montanic acid, apidic acid, 1,7-heptanedioicacid, 1,8-octandioic acid, 1,9-nonanedioic acid, sebacic acid,1,11-undecandioic acid, 1,12-dodecanedioic acid, 1,13-tridecanedioicacid, 1,14-tetradecanedioic acid, 1,15-pentadecanedioic acid,1,16-hexadecanedioic acid, 1,17-heptadecanedioic acid,1,18-octadecanedioic acid, 1,19-nonadecanedioic acid, 1,20-eicosanedioicacid, dicarboxylic acids having 21 to 40 carbon atoms, etc.

Alkylol ammonium salts of carboxylic acids (including high molecularweight carboxylic acids and unsaturated carboxylic acids) may be used.Examples include EFKA 5071, an alkylol ammonium salt of a high-molecularweight carboxylic acid supplied by Ciba and BYK-ES80, an alkylolammoniumsalt of an unsaturated acidic carboxylic acid ester manufactured by BYKUSA, Wallingford, Conn.

The charged organic compound may have a sulfur containing group such asa sulphonate, mesylate, triflate, tosylate, besylate, sulfates, sulfite,peroxomonosulfate, peroxodisulfate, pyrosulfate, dithionate,metabisulfite, dithionite, thiosulfate, tetrathionate, etc. The organiccompound may also contain two or more sulfur containing groups.

Alkyl, alkenyl, and/or alkynyl sulfates and sulphonates are preferredsulfur-containing compounds. The alkyl, alkenyl, and/or alkynyl groupspreferably contain at least about 8 carbon atoms, or more preferably atleast about 10 carbon atoms. Examples include decylsulfate salts,dodecylsulfate salts (such as sodium 1-dodecanesulfate (SDS)),decylsulfonate salts, dodecylsulfonate salts (such as sodium1-dodecanesulfonate (SDSO)), etc. The counter ions may be any suitablecation, such as lithium, sodium, potassium, ammonium, etc.

The charged organic compound may be present in about 1 to about 75weight percent, in about 2 to about 70 weight percent, in about 2 toabout 60 weight percent, in about 2 to about 50 weight percent, in about5 to about 50 weight percent, in about 10 to about 50 weight percent, inabout 10 to about 40 weight percent, in about 20 to about 40 weightpercent, based on the total weight of charged organic compound andgraphene sheets and other carbonaceous fillers, if used.

The compositions may optionally contain additional electricallyconductive components other than the graphene sheets, such as metals(including metal alloys), conductive metal oxides, polymers,carbonaceous materials other than compositions, metal-coated materials,etc. These components can take a variety of forms, including particles,powders, flakes, foils, needles, etc.

Examples of metals include, but are not limited to silver, copper,aluminum, platinum, palladium, nickel, chromium, gold, bronze, colloidalmetals, etc. Examples of metal oxides include antimony tin oxide andindium tin oxide and materials such as fillers coated with metal oxides.Metal and metal-oxide coated materials include, but are not limited tometal coated carbon and graphite fibers, metal coated glass fibers,metal coated glass beads, metal coated ceramic materials (such asbeads), etc. These materials can be coated with a variety of metals,including nickel.

Examples of electrically conductive polymers include, but are notlimited to, polyacetylene, polyethylene dioxythiophene (PEDOT),poly(styrenesulfonate) (PSS), PEDOT:PSS copolymers, polythiophene andpolythiophenes, poly(3-alkylthiophenes),poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT),poly(phenylenevinylene), polypyrene, polycarbazole, polyazulene,polyazepine, polyflurorenes, polynaphthalene, polyisonaphthalene,polyaniline, polypyrrole, poly(phenylene sulfide), copolymers of one ormore of the foregoing, etc., and their derivatives and copolymers. Theconductive polymers may be doped or undoped. They may be doped withboron, phosphorous, iodine, etc.

Examples of carbonaceous materials other than graphene sheets andgraphite include, but are not limited to, graphitized carbon, carbonblack, carbon fibers and fibrils, carbon whiskers, vapor-grown carbonnanofibers, metal coated carbon fibers, carbon nanotubes (includingsingle- and multi-walled nanotubes), fullerenes, activated carbon,carbon fibers, expanded graphite, expandable graphite, graphite oxide,hollow carbon spheres, carbon foams, etc.

Such as when they are in the form of coatings and inks, the compositionscan be applied to a wide variety of substrates, including, but notlimited to, flexible and/or stretchable materials, silicones and otherelastomers and other polymeric materials, metals (such as aluminum,copper, steel, stainless steel, etc.), adhesives, fabrics (includingcloths) and textiles (such as cotton, wool, polyesters, rayon, etc.),clothing, glasses and other minerals, ceramics, silicon surfaces, wood,paper, cardboard, paperboard, cellulose-based materials, glassine,labels, silicon and other semiconductors, laminates, corrugatedmaterials, concrete, bricks, and other building materials, etc.Substrates may in the form of films, papers, wafers, largerthree-dimensional objects, etc.

The substrates may have been treated with other coatings (such aspaints) or similar materials before the compositions are applied.Examples include substrates (such as PET) coated with indium tin oxide,antimony tin oxide, etc. They may be woven, nonwoven, in mesh form; etc.They may be woven, nonwoven, in mesh form; etc.

The substrates may be paper-based materials generally (including paper,paperboard, cardboard, glassine, etc.). Paper-based materials can besurface treated. Examples of surface treatments include coatings such aspolymeric coatings, which can include PET, polyethylene, polypropylene,acetates, nitrocellulose, etc. Coatings may be adhesives. The paperbased materials may be sized.

Examples of polymeric materials include, but are not limited to, thosecomprising thermoplastics and thermosets, including elastomers andrubbers (including thermoplastics and thermosets), silicones,fluorinated polysiloxanes, natural rubber, butyl rubber,chlorosulfonated polyethylene, chlorinated polyethylene,styrene/butadiene copolymers (SBR), styrene/ethylene/butadiene/stryenecopolymers (SEBS), styrene/ethylene/butadiene/stryene copolymers graftedwith maleic anhydride, styrene/isoprene/styrene copolymers (SIS),polyisoprene, nitrile rubbers, hydrogenated nitrile rubbers, neoprene,ethylene/propylene copolymers (EPR), ethylene/propylene/diene copolymers(EPDM), ethylene/vinyl acetate copolymer (EVA),hexafluoropropylene/vinylidene fluoride/tetrafluoroethylene copolymers,tetrafluoroethylene/propylene copolymers, fluorelastomers, polyesters(such as poly(ethylene terephthalate), poly(butylene terephthalate),poly(ethylene naphthalate), liquid crystalline polyesters, poly(lacticacid), etc).; polystyrene; polyamides (including polyterephthalamides);polyimides (such as Kapton®); aramids (such as Kevlar® and Nomex®);fluoropolymers (such as fluorinated ethylene propylene (FEP),polytetrafluoroethylene (PTFE), poly(vinyl fluoride), poly(vinylidenefluoride), etc.); polyetherimides; poly(vinyl chloride); poly(vinylidenechloride); polyurethanes (such as thermoplastic polyurethanes (TPU);spandex, cellulosic polymers (such as nitrocellulose, cellulose acetate,etc.); styrene/acrylonitriles polymers (SAN);arcrylonitrile/butadiene/styrene polymers (ABS); polycarbonates;polyacrylates; poly(methyl methacrylate); ethylene/vinyl acetatecopolymers; thermoset epoxies and polyurethanes; polyolefins (such aspolyethylene (including low density polyethylene, high densitypolyethylene, ultrahigh molecular weight polyethylene, etc.),polypropylene (such as biaxially-oriented polypropylene, etc.); Mylar;etc. They may be non-woven materials, such as DuPont Tyvek®. They may beadhesive or adhesive-backed materials (such as adhesive-backed papers orpaper substitutes). They may be mineral-based paper substitutes such asTeslin® from PPG Industries. The substrate may be a transparent ortranslucent or optical material, such as glass, quartz, polymer (such aspolycarbonate or poly(meth)acrylates (such as poly(methyl methacrylate).

The compositions may be applied to the substrate using any suitablemethod, including, but not limited to, painting, pouring, spin casting,solution casting, dip coating, powder coating, by syringe or pipette,spray coating, curtain coating, lamination, co-extrusion, electrospraydeposition, ink-jet printing, spin coating, thermal transfer (includinglaser transfer) methods, doctor blade printing, screen printing, rotaryscreen printing, gravure printing, lithographic printing, intaglioprinting, digital printing, capillary printing, offset printing,electrohydrodynamic (EHD) printing (a method of which is described in WO2007/053621, which is hereby incorporated herein by reference),microprinting, pad printing, tampon printing, stencil printing, wire rodcoating, drawing, flexographic printing, stamping, xerography,microcontact printing, dip pen nanolithography, laser printing, via penor similar means, etc. The compositions can be applied in multiplelayers.

After they have been applied to a substrate, the coatings may be curedusing any suitable technique, including drying and oven-drying (in airor another inert or reactive atmosphere), UV curing, IR curing, drying,crosslinking, thermal curing, laser curing, IR curing, microwave curingor drying, sintering, and the like.

In some embodiments, the curing may be thermal curing and may take placeat a temperature of no more than about 135° C., or no more than about120° C., or no more than about 110° C., or no more than about 100° C.,or no more than about 90° C., or no more than about 80° C., or no morethan about 70° C.

The coated substrate can be electrically conductive. It can have aconductivity of at least about 10⁻⁸ S/m. It can have a conductivity ofabout 10⁻⁶ S/m to about 10⁵ S/m, or of about 10⁻⁵ S/m to about 10⁵ S/m.In other embodiments of the invention, the coating has conductivities ofat least about 0.001 S/m, of at least about 0.01 S/m, of at least about0.1 S/m, of at least about 1 S/m, of at least about 10 S/m, of at leastabout 100 S/m, or at least about 1000 S/m, or at least about 10,000 S/m,or at least about 20,000 S/m, or at least about 30,000 S/m, or at leastabout 40,000 S/m, or at least about 50,000 S/m, or at least about 60,000S/m, or at least about 75,000 S/m, or at least about 10⁵ S/m, or atleast about 10⁶ S/m.

In some embodiments, the surface resistivity of the coated substrate maybe no greater than about 10000 Ω/square, or no greater than about 5000Ω/square, or no greater than about 1000 Ω/square or no greater thanabout 700 Ω/square, or no greater than about 500 Ω/square, or no greaterthan about 350 Ω/square, or no greater than about 200 Ω/square, or nogreater than about 200 Ω/square, or no greater than about 150 Ω/square,or no greater than about 100 Ω/square, or no greater than about 75Ω/square, or no greater than about 50 Ω/square, or no greater than about30 Ω/square, or no greater than about 20 Ω/square, or no greater thanabout 10 Ω/square, or no greater than about 5 Ω/square, or no greaterthan about 1 Ω/square, or no greater than about 0.1 Ω/square, or nogreater than about 0.01 Ω/square, or no greater than about 0.001Ω/square.

The coated substrate can have a thermal conductivity of about 0.1 toabout 50 W/(m-K), or of about 0.5 to about 30 W/(m-K), or of about 1 toabout 30 W/(m-K), or of about 1 to about 20 W/(m-K), or of about 1 toabout 10 W/(m-K), or of about 1 to about 5 W/(m-K), or of about 2 toabout 25 W/(m-K), or of about 5 to about 25 W/(m-K).

When applied to a substrate, the compositions can have a variety ofthicknesses. In one embodiment, when applied to a substrate, aftercuring the coating can optionally have a thickness of at least about 2nm, or at least about 5 nm. In various embodiments, the coatings canoptionally have a thickness of about 2 nm to 2 mm, about 5 nm to 1 mm,about 2 nm to about 100 nm, about 2 nm to about 200 nm, about 2 nm toabout 500 nm, about 2 nm to about 1 micrometer, about 5 nm to about 200nm, about 5 nm to about 500 nm, about 5 nm to about 1 micrometer, about5 nm to about 50 micrometers, about 5 nm to about 200 micrometers, about10 nm to about 200 nm, about 50 nm to about 500 nm, about 50 nm to about1 micrometer, about 100 nm to about 10 micrometers, about 1 micrometerto about 2 mm, about 1 micrometer to about 1 mm, about 1 micrometer toabout 500 micrometers, about 1 micrometer to about 200 micrometers,about 1 micrometer to about 100 micrometers, about 50 micrometers toabout 1 mm, about 100 micrometers to about 2 mm, about 100 micrometersto about 1 mm, about 100 micrometers to about 750 micrometers, about 100micrometers to about 500 micrometers, about 500 micrometers to about 2mm, or about 500 micrometers to about 1 mm.

When applied to a substrate, the compositions can have a variety offorms. They can be present as a film or lines, patterns, letters,numbers, circuitry, logos, identification tags, and other shapes andforms. The coatings may be covered in whole or in part with additionalmaterial, such as overcoatings, varnishes, polymers, fabrics, etc.

The compositions can be applied to the same substrate in varyingthicknesses at different points and can be used to build upthree-dimensional structures on the substrate.

The compositions can be used for the passivation of surfaces, such asmetal (e.g. steel, aluminum, etc.) surfaces, including exteriorstructures such as bridges and buildings. Examples of other uses of thecompositions include: UV radiation resistant coatings, abrasionresistant coatings, coatings having permeation resistance to liquids(such as hydrocarbon, alcohols, water, etc.) and/or gases, electricallyconductive coatings, static dissipative coatings, and blast and impactresistant coatings. They can be used to make fabrics having electricalconductivity. The compositions can be used in solar cell applications;solar energy capture applications; signage, flat panel displays;flexible displays, including light-emitting diode, organiclight-emitting diode, and polymer light-emitting diode displays;backplanes and frontplanes for displays; and lighting, includingelectroluminescent and OLED lighting. The displays may be used ascomponents of portable electronic devices, such as computers, cellulartelephones, games, GPS receivers, personal digital assistants, musicplayers, games, calculators, artificial “paper” and reading devices,etc.

They may be used in packaging and/or to make labels. They may be used ininventory control and anti-counterfeiting applications (such as forpharmaceuticals), including package labels. They may be used to makesmart packaging and labels (such as for marketing and advertisement,information gathering, inventory control, information display, etc.).They may be used to form a Faraday cage in packaging, such as forelectronic components.

The compositions can be used on electrical and electronic devices andcomponents, such as housings etc., to provide EMI shielding properties.They made be used in microdevices (such as microelectromechanicalsystems (MEMS) devices) including to provide antistatic coatings.

They may be used in the manufacture of housings, antennas, and othercomponents of portable electronic devices, such as computers, cellulartelephones, games, navigation systems, personal digital assistants,music players, games, calculators, radios, artificial “paper” andreading devices, etc.

The compositions can be used to form thermally conductive channels onsubstrates or to form membranes having desired flow properties andporosities. Such materials could have highly variable and tunableporosities and porosity gradients can be formed. The coatings can beused to form articles having anisotropic thermal and/or electricalconductivities. The coatings can be used to form three-dimensionalprinted prototypes.

The compositions can be used to make printed electronic devices (alsoreferred to as “printed electronics) that may be in the form of completedevices, parts or sub elements of devices, electronic components, etc.

Printed electronics may be prepared by applying the compositions to thesubstrate in a pattern comprising an electrically conductive pathwaydesigned to achieve the desired electronic device. The pathway may besolid, mostly solid, in a liquid or gel form, etc.

The printed electronic devices may take on a wide variety of forms andbe used in a large array of applications. They may contain multiplelayers of electronic components (e.g. circuits) and/or substrates. Allor part of the printed layer(s) may be covered or coated with anothermaterial such as a cover coat, varnish, cover layer, cover films,dielectric coatings, electrolytes and other electrically conductivematerials, etc. There may also be one or more materials between thesubstrate and printed circuits. Layers may include semiconductors, metalfoils, dielectric materials, etc.

The printed electronics may further comprise additional components, suchas processors, memory chips, other microchips, batteries, resistors,diodes, capacitors, transistors, etc.

Other applications include, but are not limited to: passive and activedevices and components; electrical and electronic circuitry, integratedcircuits; flexible printed circuit boards; transistors; field-effecttransistors; microelectromechanical systems (MEMS) devices; microwavecircuits; antennas; diffraction gratings; indicators; chipless tags(e.g. for theft deterrence from stores, libraries, etc.); security andtheft deterrence devices for retail, library, and other settings; keypads; smart cards; sensors; liquid crystalline displays (LCDs); signage;lighting; flat panel displays; flexible displays, includinglight-emitting diode, organic light-emitting diode, and polymerlight-emitting diode displays; backplanes and frontplanes for displays;electroluminescent and OLED lighting; photovoltaic devices, includingbackplanes; product identifying chips and devices; membrane switches,batteries, including thin film batteries; electrodes; indicators;printed circuits in portable electronic devices (for example, cellulartelephones, computers, personal digital assistants, global positioningsystem devices, music players, games, calculators, etc.); electronicconnections made through hinges or other movable/bendable junctions inelectronic devices such as cellular telephones, portable computers,folding keyboards, etc.); wearable electronics; and circuits invehicles, medical devices, diagnostic devices, instruments, etc.

The electronic devices may be radiofrequency identification (RFID)devices and/or components thereof and/or radiofrequency communicationdevice. Examples include, but are not limited to, RFID tags, chips, andantennas. The RFID devices may be ultrahigh frequency RFID devices,which typically operate at frequencies in the range of about 868 toabout 928 MHz. Examples of uses for RFIDs are for tracking shippingcontainers, products in stores, products in transit, and parts used inmanufacturing processes; passports; barcode replacement applications;inventory control applications; pet identification; livestock control;contactless smart cards; automobile key fobs; etc.

The electronic devices may also be elastomeric (such as silicone)contact pads and keyboards. Such devices can be used in portableelectronic devices, such as calculators, cellular telephones, GPSdevices, keyboards, music players, games, etc. They may also be used inmyriad other electronic applications, such as remote controls, touchscreens, automotive buttons and switches, etc.

EXAMPLES

Unless otherwise stated, the surface resistivities are measured using aGuardian Manufacturing Inc. SRM-232 surface resistivity meter. Theresults are given in Tables 1-4. Adhesion is evaluated by firmlyapplying a piece of Scott® Magic® tape to the surface and peeling itoff. A rating of “1” means that the peeled tape is completely dark. Arating of “2” means that the peeled tape surface contains completelydark regions with a few regions where it is grey. A rating of “3” meansthat the peeled tape surface appears to be have at least about 30percent grey regions and no more than about 70 percent completely darkregions.

Examples 1-13 and Comparative Examples 1-10

Graphene sheets (about 20 weight percent) and graphite (about 80 weightpercent) are ground in a vertical grinding mill with 3/16″ stainlesssteel grinding media in isopropyl alcohol. The resulting pigment iscombined with an Elvacite® 2028, a methacrylate copolymer supplied byLucite International in a pigment to polymer weight ratio of 4:1. One ormore additional solvents are added to bring the compositions to thesolids (pigment and polymer) concentration indicated in Tables 1-3. Theamounts of each solvent used are also indicated in the tables.

The resulting formulations are printed onto uncoated poly(ethyleneterephthalate) films in the case of Examples 1-2 and 12-13 andComparative Examples 1-6 and on poly(ethylene terephthalate) coatedpaperboard in the case of Examples 3-11 and Comparative Examples 7-10.The prints are cured in an infrared oven at 80° C. for about 1 minute inthe case of Examples 1-11 and Comparative Examples 1-10 and for about 2minutes in the case of Examples 12-13. The results are given in thetables.

Examples 14-18 and Comparative Example 11

Graphene sheets (about 20 weight percent) and graphite (about 80 weightpercent) are ground in a bead mill in hexanol. The resulting pigment iscombined with poly(vinyl butyral) in pigment to polymer weight ratio of4:1. One or more additional solvents are added to bring the compositionsto the solids (pigment and polymer) concentration indicated in Table 4.The amounts of each solvent used are also indicated in the table.

The resulting formulations are screen printed onto uncoatedpoly(ethylene terephthalate) films and are cured in an infrared oven at130° C. for about 6 minutes. The results are given in Table 4.Resistivity measurements are the averages of measurements taken onseveral prints.

Examples 19-21 and Comparative Example 12-16

Graphene sheets (about 20 weight percent), graphite (about 80 weightpercent), and solver flakes are ground in a vertical grinding mill with3/16″ stainless steel grinding media in hexanol. The relativeproportions of carbon (graphene sheets and graphite) and silver areindicated in Table 5. The resulting pigment is combined with poly(vinylbutyral) in pigment to polymer weight ratio of 4:1. One or moreadditional solvents are added to bring the compositions to the solids(pigment and polymer) concentration indicated in Table 5. The amounts ofeach solvent used are also indicated in the table.

The resulting formulations are screen printed onto uncoatedpoly(ethylene terephthalate) films and are cured in an infrared oven at130° C. for about 6 minutes. The results are given in Table 5. Thesurface resistivities are determined by measuring 100 and 50 squarelines using an ohmmeter. Resistivity measurements are the averages ofmeasurements taken on several prints.

TABLE 1 Comp. Comp. Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 1 Ex.4 Ex. 5 Ex. 6 Ex. 2 Solids 7.3 7.3 7.3 7.3 7.3 7.3 7.3 7.3 IPA 92.7 82.782.7 82.7 74.7 64.7 64.7 64.7 nBuOAc — — — — 18 18 18 18 nBuOH — 10 — —— 10 — — Diglyme — — 10 — — — 10 — γ-Butyrolactone — — — 10 — — — 10Surface 134 66 41 34 45 56 40 35 resistivity (Ω/sguare) Adhesion 1 1 2 31 1 2 3 Ingredient amounts are in weight percent based on the totalweight of the composition.

TABLE 2a Comp. Comp. Ex. 7 Ex. 3 Ex. 4 Ex. 8 Ex. 5 Ex. 6 Solids 5.0 5.05.0 5.0 5.0 4.9 IPA 95.0 84.8 75.0 85.0 75.2 64.7 nBuOAc — — — — — —nBuOH — — — 10.0 9.9 10.0 γ-Butyrolactone — 10.2 20.0 — 9.9 20.4 Surface233 74 68 91 54 60 resistivity (Ω/sguare) Adhesion 1 3 3 1 3 3Ingredient amounts are in weight percent based on the total weight ofthe composition.

TABLE 2b Comp. Comp. Ex.9 Ex. 7 Ex. 8 Ex. 10 Ex. 9 Ex. 10 Ex. 11 Solids5.0 5.0 4.9 5.0 4.9 5.0 4.9 IPA 75.1 64.7 54.2 64.9 54.4 44.9 55.8nBuOAc — — — — — — 10.9 nBuOH 20.0 19.9 19.8 30.1 30.8 30.3 19.8γ-Butyrolactone — 10.4 21.1 — 9.9 19.8 9.7 Surface 102 61 59 138 46 6079 resistivity (Ω/sguare) Adhesion 1 2 3 1 3 3 2 Ingredient amounts arein weight percent based on the total weight of the composition.

TABLE 3 Ex. 12 Ex. 13 Solids 5 5 IPA 74.6 74.4 nBuOAc 5.2 5.3 NMP — 5.1λ-Butyrolactone 15.3 10.2 Surface resistivity 39 31 (Ω/square) Adhesion3 3 Ingredient amounts are in weight percent based on the total weightofthe composition.

TABLE 4 Comp. Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex. 11 Solids 15.6 15.615.6 15.6 15.6 15.6 nHexOH 77.4 72.4 67.4 53.4 53.2 84.4 NMP 7 12 17 317 — α-Terpineol — — — — 24.2 — Surface 38 36 33 34 37 84 resistivity(Ω/sguare) Adhesion 3 3 3 3 3 2 Ingredient amounts are in weight percentbased on the total weight of the composition.

TABLE 5 Comp. Comp. Comp. Comp. Comp. Ex. 19 Ex. 12 Ex. 20 Ex. 13 Ex. 21Ex. 14 Ex. 15 Ex. 16 Silver 5.3 5.3 9.2 9.2 17.1 17.3 36 36 Carbon 12.312.3 9.2 9.2 7.3 7.4 — — Binder 4.4 4.4 4.6 4.6 6.1 6.2 9 9 Hexanol 58.178 57.1 77.1 49.4 69.1 35 55 NMP 20 — 20 — 20 — 20 — Surface 14 34 15 291.2 1.2 0.3 0.3 resistivity (Ω/square) Adhesion 1 1 3 2 3 3 3 3Ingredient amounts are in weight percent based on the total weight ofthe composition.

The invention claimed is:
 1. A composition comprising graphene sheets, graphite, at least one binder, and a carrier system, wherein about 1 to about 50 weight percent of the carrier system comprises at least one cyclic imide and/or lactone and wherein the ratio by weight of graphite to graphene sheets is from about 50:50 to about 85:15.
 2. The composition of claim 1, wherein the carrier system comprises about 1 to about 40 weight percent of at least one cyclic imide and/or lactone.
 3. The composition of claim 1, wherein the carrier system comprises about 3 to about 40 weight percent of at least one cyclic imide and/or lactone.
 4. The composition of claim 1, wherein the binder is one or more selected from acrylate polymers, polyamides, and poly(vinyl butyral).
 5. The composition of claim 1, wherein the carrier system comprises gamma-butyrolactone.
 6. The composition of claim 1, further comprising silver.
 7. The composition of claim 1, wherein the graphene sheets have a surface area of at least about 400 m²/g.
 8. The composition of claim 1, wherein the graphene sheets have a surface area of at least about 500 m²/g.
 9. The composition of claim 1, wherein the graphene sheets have a carbon to oxygen ratio of at least about 10:1.
 10. The composition of claim 1, wherein the graphene sheets have a carbon to oxygen ratio of at least about 25:1.
 11. The composition of claim 1, wherein the graphene sheets have a carbon to oxygen ratio of at least about 75:1.
 12. The composition of claim 1 in the form of an ink or coating.
 13. The composition of claim 1, wherein from about 1 to about 30 weight percent of the carrier system comprises at least one cyclic imide and/or lactone.
 14. The composition of claim 1, wherein from about 5 to about 40 weight percent of the carrier system comprises at least one cyclic imide and/or lactone.
 15. The composition of claim 1, wherein from about 5 to about 30 weight percent of the carrier system comprises at least one cyclic imide and/or lactone. 